The h Bar

I really don't get why people were attacking me early for critisizing heather's ad, I was just pointing out obvious design flaws and everyone got so furious.

@SirCumference did you see the ad? and thoughts?

0celo7

because you wouldn't drop it

Sir Cumference

@obe I liked hers, it was a pretty simplistic idea imo

obe

not talking about the idea.

Sir Cumference

Way less convoluted than my astro one

obe

1:05 AM

let me see yours.

Sir Cumference

Here's mine from last year

heather

that's a good ad

Sir Cumference

I plan to do a lot better this year

obe

dude that's quite alright

heather

wait, sorry: is that the death star, or a moon that looks like the death star? I know that miranda has those gouges that could look like the death star, but.

0celo7

1:07 AM

what is a death star?

ACuriousMind

@heather Well, it's not a question that comes up often ordinarily (and it is actually more subtle to answer than one might think), but the standard foundation goes like this: We have to start somewhere, so we define logical expressions "manually" by what is called a truth table. It's a lookup table that tells you what the logical operator (like 'and', 'if', 'or') yields for any given combination of truth values for its input

Sir Cumference

The better version, which I was too lazy to upload, is here

heather

@0celo7 Star Wars

Sir Cumference

ACuriousMind

For a programmer's mind: "truth value" = Boolean.

0celo7

1:07 AM

@heather sounds violent

3

Sir Cumference

@heather Was supposed to be mimas

heather

@ACuriousMind oh, yeah, i've seen those used for logic gates.

@SirCumference oh, okay.

Sir Cumference

@heather No one can tell XD

heather

@0celo7 you seriously haven't heard of star wars?

obe

@SirCumference have you ever heard of different blending options?

ACuriousMind

1:08 AM

@heather Very nice! So 'if' is just a special kind of logic gate, and that's its definition

heather

so if is defined by its truth table?

Sir Cumference

@obe Hadn't at the time. In the year between I've actually looked into photoshop tutorials, instead of relying on what I'd picked up over the years

ACuriousMind

Of course, if you know how to combine truth tables, you can then also define 'iff' and more complicated expressions by their truth tables, but once you've defined the basic things like 'and', 'or', 'if' one usually drops that as it becomes rather laborious and unenlightening

obe

@SirCumference look at your galaxy in the top right, if you had applied radial feathering and changed the blending option to "lighten" it would look more realistic.

Sir Cumference

@obe Yes, yes, I know

heather

1:09 AM

@ACuriousMind what is the truth table for if?

::googles::

0celo7

@ACuriousMind Rebecca is taking a class on logic and set theory and this stuff blows my mind

I don't know it makes sense to people

ACuriousMind

@heather The formal name of if is logical implication

Sir Cumference

@obe So, uh, could you send the logo?

heather

if p is true, then q is true.

wait, ack. i'm confused now.

Sir Cumference

13

Q: "If" vs "Only if" vs "If and only if"

If I said: Yell only if I fall. Would the person have to yell once I fell? Sources of confusion Wikipedia This guy

heather

1:11 AM

what's q?

@SirCumference huh, interesting.

@ACuriousMind, help, this truth table makes no sense.

obe

@heather well basically it's saying that if you have a a true statement it can't result in a false statement. but a false statement can imply any statement.

ACuriousMind

@heather Yes, that is approximately the reaction of 75% of people when they first see the table for if :)

4

heather

if you have the reaction of 75% of people, then that is the reaction you have.

::tries to break formal logic::

okay, so what does it mean...

0celo7

@heather It should be noted that I disagree with that table.

ACuriousMind

@heather You're thinking that the parts where P is false make no sense, right?

heather

1:14 AM

@0celo7 truth tables are arguable?

0celo7

100%

heather

@ACuriousMind no, i'm wondering what the heck q is and why it has a value.

0celo7

ACM is one of the sheeple who thinks the P false part makes sense.

heather

i mean, those don't make sense either, but.

obe

@heather what do you mean what is it?

ACuriousMind

1:16 AM

@heather In "If it rains, the ground is wet", Q="The ground is wet" and P="It rains".

obe

it's a statement. which is basically something that can be assigned T or F but not both.

heather

@ACuriousMind okay...*::thinks::*

0celo7

@obe law of excluded middle is false

proofs by contradiction are false

heather

so it's evaluating whether each phrase and then the total statement is false.

let me look at the truth table again.

0celo7

there are real numbers which are neither rational nor irrational

it's all a conspiracy

heather

1:17 AM

actually, i think the latter two in the table make sense.

it's like...the statement hasn't been tested. so we keep assuming it's true.

because the statement is if p, then q.

ACuriousMind

@heather It's not evaluating the individual phrases. It's given the truth (or falsity) of the individual phrases as input and then decides whether the total "If P, then Q" is true or false

heather

^that's what I meant.

ACuriousMind

@heather Yes! I like to call the table "falsificationist's if", and that's exactly what it means.

Congrats, you're a natural at logic ;)

heather

if if p is false, then we can't say that if p then q is false, because the statement is dependent on if p being true.

@ACuriousMind I get something in logic for once!

and my parents always say I'm illogical. hah.

obe

@heather think of it this way and it will make sense to you. $P \implies Q := (\neg P) \lor Q$

0celo7

1:19 AM

@dmckee thermo god, pls assist

heather

@obe wat

could you speak english please?

0celo7

@heather I agree

obe

seriously?

heather

I don't know what :=, -| and V mean.

obe

google it

0celo7

1:20 AM

@obe I don't know either

heather

not easily googlable symbols, but very well.

yes you do.

I don't

:= means defined as.

Jesus christ, you people aren't helpful

heather

1:21 AM

v means or, apparently.

0celo7

@SirCumference are you good at thermo

Sir Cumference

@obe You thought that would be easier for her?

obe

yes

let me explain

0celo7

@obe ok I will be as helpful as you in the future

heather

and then -| means negation

kay, so dunno why you've got the arrow. but Q is defined as not-P or Q.

Sir Cumference

1:22 AM

@heather Ok, "A if B means that B implies A."

heather

@SirCumference, right.

Q is defined as, that makes sense.

wait, why are you defining Q as that?

not-P the negation of P.

Sir Cumference

@heather Say I tell you that "It is wet if it is raining". By knowing that it is raining, you know it's wet.

heather

@ACuriousMind, you are much better at this than obe, no offense @obe.

@SirCumference yeah.

Sir Cumference

But you don't know it is raining just by knowing it's wet. It could be wet, for example, because the sprinklers were going off outside.

heather

right.

ACuriousMind

1:24 AM

Wait, we were there already

Sir Cumference

@ACuriousMind Oh nvm then, I wasn't reading that

0celo7

@dmckee Seriously, I need help. I have water at 70psia and enthalpy 91.234 Btu/lbm. I checked the tables and the enthalpy of formation for water at that pressure is 272. So it's a compressed liquid

obe

@heather $P \implies Q := (\neg P) \lor Q$ means that $P$ implies $Q$ is defined as the negation of $P$ and/or $Q$. so basically that statement is true if either the negation of $P$ is true or if $Q$ is true. therefore the statement $P \implies Q$ is true if both $P$ and $Q$ are true and if $P$ is false regardless of weather $Q$ is true or not.

Sir Cumference

Not sure what you're confused on, but @ACuriousMind is helping you. You'll be fine.

0celo7

@dmckee But my compressed liquid tables don't go that low for pressures

Sir Cumference

1:25 AM

@obe, on the other hand...

0celo7

@dmckee So I'm trying to approximate as a saturated liquid, but I don't know the pressure

Sir Cumference

@0celo7 You like stellar physics?

0celo7

@dmckee So if i take the sat temp for that pressure, I get the wrong enthalpy back

so that can't be right

ACuriousMind

@heather I'm not entirely sure why obe brought this up but by the power of truth tables you can show that the expressions "If P, then Q" and "(not P) or Q" are equivalent. People who want to avoid truth tables as much as possible therefore might only define 'and', 'or' and 'not' by truth tables and then define 'if' by "(not P) or Q".

Sir Cumference

@0celo7 or cosmology

0celo7

1:27 AM

@SirCumference I used to like cosmology

Sir Cumference

@0celo7 but then?

heather

if p then q is the same as not p or q?

0celo7

Math is better

Sir Cumference

@0celo7 ...

obe

@heather yes that's how it's defined.

Sir Cumference

1:27 AM

Cosmology is so darn cool tho

ACuriousMind

However, that definition of if usually takes even more convincing to get people to accept than the truth table

heather

i don't get that definition.

ACuriousMind

@obe No, I can also just write down the truth table for the implication and say 'if' is defined by that. It's a matter of choice.

heather

let's just stick with the truth table.

it makes more sense.

0celo7

@dmckee So now I'm thinking I should interpolate the temperature given the enthalpy, ignoring the pressure

obe

1:28 AM

well if you use the expression form it's also useful in proofs.

0celo7

by just using the saturated liquid tables

Sir Cumference

@0celo7 Well do you know some stuff on cosmology?

0celo7

why

ACuriousMind

@heather Well, but there's an interesting point here: Different logical expressions can have the same truth table.

Sir Cumference

Need help with some stuff

heather

1:29 AM

@ACuriousMind huh, like what?

0celo7

I can teach you general relativity

heather

i can see that happening, just like different equations can have the same solutions or graph or whatever.

ACuriousMind

@heather Consider "not(not(P))" and "P" (separate expressions, not a logical and)

heather

@ACuriousMind oh, those are the same.

that makes sense.

Sir Cumference

@0celo7 That's not what I asked

heather

1:30 AM

the nots cancel.

obe

proof?

xD

heather

@0celo7 =)

ACuriousMind

@heather Exactly, but the way you formally know/prove they are the same is by writing down their truth tables and observing they are the same!

0celo7

@SirCumference what did you ask

heather

@ACuriousMind huh, okay, cool!

Sir Cumference

1:31 AM

@0celo7 I need clarification on something regarding the observable universe

heather

so the truth table for P would be like

obe

@SirCumference how long are you gonna remain a popsci boy? xD

0celo7

just ask the damn question

Sir Cumference

@obe Screw off...I'm actually dealing with the equations

heather

P | P
-----
T | T
F | F

obe

1:31 AM

the language of cosmology is GR, so why the fuck are you not accepting his offer to teach you GR? @SirCumference

just curious.

0celo7

language

ACuriousMind

@heather Yep

Sir Cumference

@obe We're getting to the details in class

0celo7

that's the langauge that got me thrown in the gulag

obe

you're taking GR?

0celo7

1:32 AM

so better not do it

Sir Cumference

Not to its entirety. More so just a few things

heather

P | not P
----------
T | F
F | T

ACuriousMind

@obe Please stay calm, you're coming off a bit aggressive

obe

well 0celo7 is offering to teach it to you properly so you can actually use it to think for yourself and answer your own questions not just memorize equations.

@ACuriousMind everyone always tells that to me.

heather

P | not not P
--------------
T | T
F | F

obe

1:33 AM

but I'm calm af.

heather

@ACuriousMind but that doesn't feel like a proof

Sir Cumference

@obe Dude, I'm struggling as it is on a lot of the geometry, etc.

Slereah

hey hey

heather

that feels like me using the same intuition i used before only this time i'm making it a table.

Sir Cumference

0celo is known to amp up the difficulty tenfold

Unless he's teaching heather

obe

1:34 AM

@SirCumference yes I know, I can relate with you on that in some cases.

0celo7

@SirCumference because she's actually nice

obe

SirCumference is nice too though.

Sir Cumference

:D

0celo7

What does that even mean?

obe

In fact I felt like heather was being mean to me today but acting like I was being mean to her. which in fact I was not.

not very nice.

Sir Cumference

1:37 AM

@obe Riemannian geometry is weird too

0celo7

what is wrong with Riemannian geometry?

obe

huh?

Sir Cumference

It's bad because I hated high school geometry

And all this is going too damn fast

obe

are you at CUNY?

Sir Cumference

@obe Nope

obe

1:38 AM

I found a friend there recently.

Sir Cumference

I've barely had time to write the notes, let alone look over them

ACuriousMind

@obe Then maybe there is truth to that? If everyone perceives you as aggressive it matters little that that doesn't match your subjective impression

@heather What must a proof "feel" like?

Sir Cumference

I'm in essence a bit jelly of you two for understanding it properly

obe

lol I don't understand it "properly" if you're talking about me.

I just know the basics

Sir Cumference

Well, at least @0celo7

obe

1:40 AM

yes i'm jelly too.

but then again idek what I wanna do in life so I'm not really jelly right now.

0celo7

Riemannian geometry has nothing to do with high school geometry

I once derived high school geometry from Riemannian geometry, and it was terrible

Sir Cumference

@0celo7 Welp, I guess I have no justification for sucking at it

obe

@SirCumference read carroll.

I read up to ch4 (or 5?) and it was good.

Sir Cumference

@obe I guess I'll try

obe

and he has examples in cosmology in most chapters.

@ACuriousMind For some reason everyone thinks being cynical or constantly giving feedback they don't want to hear is aggressive.

Sir Cumference

1:45 AM

@obe I think you should've given heather credit for a nice idea. She's a better artist than me, too.

obe

I basically get motivated off bad feedback or putdowns, but maybe that's just me.

Sir Cumference

@0celo7 So, uh, do you know cosmology?

obe

@SirCumference but it wasn't a nice idea, it's basically the first thing that would come to anyone's mind.

Sir Cumference

@obe Guess we'll disagree.

obe

why do you keep going back to that, it's done.

@SirCumference or actually can you refute me and reason why it was a good idea?

what was creative about it, or what made it special?

just curious.

heather

1:48 AM

@obe um, I apologize if I came across that way, but you were rather blatantly criticizing the ad and refused to give any specific advice until 15/16ths of the way through the conversation.

Sir Cumference

@obe I guess, though I'm not sure that it's appropriate in the middle of the chat. I thought hers was a nice and simple representation of astronautics. All it needs is to be touched up on.

0celo7

@heather In obe's defense, I understood his criticism from the beginning and was very confused why people kept asking him what the problem was.

Sir Cumference

We don't need more than that, really.

heather

@ACuriousMind I don't know...maybe more like there's some specified rules and steps? something between you and your intuition?

obe

@heather yeah I'm sorry too, it's just that sometimes I feel like when something seems obvious to me it seems obvious to everyone else too.

0celo7

1:49 AM

Because he said very clearly what it was.

heather

@0celo7 the criticism that something "isn't professional" is a bit broad and doesn't come to me as clear, especially as someone who has no clue what "professional" looks like. ::shrugs::

Sir Cumference

Ugh goddammit

I'm looking across all kinds of SE chats, no one knows about stellar physics

ACuriousMind

@obe 1. Yes, being cynical comes off as aggressive or mean to people you don't know well, especially on the internet where there are no non-verbal cues. It takes good social calibration to know when youcan be cynical.

2. Also, yes, people don't want to hear things they don't want to hear. If you know they don't want to hear it, it will come off as aggressive regardless of whether it is true or not. The art of giving feedback is not merely to recognize what you want to say but also how you want to say it

obe

@heather a professional design implements a lot of things, first of all it looks clean and focuses on small details as much as large ones, and it also makes use of a lot of design aspects and techniques while also making use of professional programs that allow you to implement all those things properly and clearly.

heather

@obe if you had said that earlier, I think your criticism would've sounded a lot less harsh.

obe

1:52 AM

:p

heather

but, oh, well. the ad's posted, you can downvote it if you want =)

Sir Cumference

@0celo7 Is it true you wear an eyepatch, btw?

heather

@ACuriousMind, what does the direction part of 0celo's proof mean?

0celo7

@SirCumference Yes, for a few more days

obe

like I said, I explain things like they don't need much explaining since they're obvious to me so they must be obvious to other people.

I need to work on that.

Sir Cumference

1:53 AM

@0celo7 That's good. Bernard made it sound like you lost an eye.

0celo7

Almost did

obe

@heather do you want me to make an identical version of your ad, but properly? this isn't related to the other one I'm going to make.

heather

@obe I do that sometimes too. It's not a big deal, and I apologize for over-reacting earlier, because looking back at the transcript, I kind of did.

obe

just to explain what I mean.

Sir Cumference

@0celo7 Jesus, what happened?

heather

1:54 AM

@obe if you want too, sure, go ahead. I don't want to take up your time or anything.

0celo7

@SirCumference I can't say, we have a no politics rule.

heather

I wouldn't mind seeing it, for sure.

Sir Cumference

what

obe

all my time is free time. as long as I don't have a problem set due in < 1 day.

heather

@0celo7 uh...oh gosh.

Sir Cumference

1:54 AM

@0celo7 You got into a political fight?

heather

@obe sure, then, if you want to make it, I would be glad for the comparison.

0celo7

@SirCumference Do you want me to get banned again?

They will delete my account.

ACuriousMind

@heather Which one again? You're right, we disgressed into foundations of logic because we wanted to understand a proof

obe

@heather can you link it again please?

Sir Cumference

.-.

obe

1:55 AM

the one you posted.

0celo7

@SirCumference I can text you if you wish

obe

@ACuriousMind I agree with everything you're saying, I'm working on improving.

heather

2

A: Community Promotion Ads - 2017

Sir Cumference

@0celo7 Er, not really tempted to give my number away on a chat

heather

@ACuriousMind um, let me find it.

ACuriousMind

1:56 AM

@0celo7 FWIW, accounts are only deleted on user request or if you're a blatant abuser of the system like a spammer.

heather

1 hour ago, by 0celo7

You need to prove two directions, and I am indicating which direction I am proving.

0celo7

@ACuriousMind Really? David Z once wrote me a note saying account deletion was a possibility. Although maybe I am misremembering.

heather

And then I asked what it meant to prove in directions.

0celo7

@heather I had hoped we could have defined measure on a sigma ring today :(

But it appears you need a lot more background

heather

well, depends on how you define today @0celo7 =)

0celo7

1:58 AM

today ends in 3 hours

I'd better get on that lab report

heather

what do i need to understand by the time we next talk? (if you just want me to keep reading halmos, that's fine too)

ACuriousMind

@0celo7 Ah, yeah, the official guidelines do say it's possible, but it occurs basically never, and certainly not to accounts with as many contributions as yours. However, getting banned by a CM for 10 years is also a possibility and basically equivalent from the user's viewpoint, so...

0celo7

@ACuriousMind I don't suppose you could use your mod powers to get Mafia's old email? I want to talk to him

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